The present invention is directed generally to aircraft avionics flight data recorder systems and methods for accident and incident investigation and, more particularly, to cost reduction methods for flight data recording systems including new data recording methods and methods for building and certifying flexible recording systems without the need for costly re-certification efforts.
With each latest rulemaking by national and international Aircraft Regulatory agencies new requirements are mandated for recording flight data using a Flight Data Recorder System (FDRS). In one embodiment the FDRS, consists of the Flight Data Recorder (FDR) and the Flight Data acquisition unit (FDAU). This system is used for recording data associated with various aircraft parameters. The FDRS is primarily an investigative tool for reconstructing and evaluating the performance of an aircraft prior to and during an accident or incident. During an investigation, the data recorded in the FDR is used to better assist the investigation of such accidents and incidents.
The FDAU acquires and the FDR records aircraft parameters at a predetermined sampling rate and may, in some instances, filter the recorded data. The FDRS may be used to record data associated with an aircraft's flight control systems such as, for example, pitch angle, roll angle, airspeed, elevator position, aileron position, control wheel position, rudder position, and radio altitude, among other types of aircraft data and/or parameters. For example, the FDRS may be used to record event signals that may be associated with one or more aircraft parameters such as engine hydraulic system data from a pressure switch or sensor, brake pressure data from a pressure sensor, aircraft ground/air speed data, flight number/leg data, aircraft heading data from an Inertial Reference Unit (IRU) and/or Electronic Flight Instrument System (EFIS), weight-on-wheels or weight-off-wheels data from an air/ground relay, Greenwich Mean Time (GMT) from the captain's clock, and other similar event signals such as door open/closed sensors, and the like.
The FAA and National Transportation Safety Board (NTSB) often issue safety recommendations and requirements for new regulations and frequently includes mandates for sampling and recording parameters at increasingly higher sampling and recording rates. These higher sampling and recording mandates generally increase the volume of recorded data beyond the capacity of an aircraft's existing FDR and often requires the replacement of the FDR or the complete FDR system. Present implementations of FDRS, however, treat the sampling rates and recording rates as one requirement. Thus, any increase in the sampling rate results in a direct increase in the recording rate and thus a direct increase in the volume of storage required in the FDR to store the data, and a direct increase in the bandwidth of the information channel between the FDAU and the FDR.
Non-deterministic and deterministic data compression are ways to decrease the overall storage requirements of the FDR. Conventional non-deterministic data compression systems and methods, however, are prone to circumstances where the data compression produces little or no advantage. Furthermore, it is difficult if not impossible to calculate the required minimum storage capacity based on non-deterministic data compression techniques to satisfy all possible changes in the data. This is because it is difficult to determine ahead of time how much the data will be compress, and thus is difficult to provide a FDR with a minimum storage capacity to handle changes in the data. Without the ability to calculate the minimum storage requirements ahead of time, a mandatory flight data recording system would not benefit fully simply by this data compression alone and would be forced to allocate minimum storage for the worst-case scenario. Furthermore, some conventional non-deterministic data compression methods require a certain amount of data to be buffered before compression can be applied. Conventional non-deterministic compression techniques, therefore, fail to meet the requirements imposed on FDRS where the data must be transferred to crash protected media within fractions of a second after being sampled. Thus, conventional non-deterministic compression techniques may free up little or no storage volume for recording the additional data at the higher sampling rates.
Conventional deterministic methods may be used to reduce the volume of recorded data by packing the aircraft parameters into words, bus-switching the parameters, and dropping the less significant bits of parameters. Although these conventional deterministic methods reduce the required volume of storage, used alone they do not provide an adequate solution to the increased storage requirements.
Thus, there is a need in the art for a system and method for recording aircraft related data at the mandated higher sampling rates without the need for a proportional increase in the bandwidth and storage capacity of and without the need to completely replace an existing FDR, which may be costly to do in either case. Accordingly, there is a need in the art for systems and methods that can accommodate the mandated higher sampling rates that utilize the existing FDR data storage capacity for recording the higher volume of data produced by the higher sampling rates. Such systems and methods might prevent the costly upgrade of the FDR hardware and thus lead to significant cost savings.
The EUROCAE document ED112 provides a likely basis for any European rulemaking with respect to recording flight data for accident and/or incident investigation. Section 1-1.3.5 of this document provides that it is highly desirable to have voluntary parameters recorded alongside the mandatory parameters on the crash protected FDR. The recording system for the mandatory parameters is subject to costly certification efforts anytime a change is made. On the other hand, the recording of voluntary parameters merely requires some flexibility in allowing operators to make changes as needed, sometime even on a daily basis. Accordingly, there is need in the art for a system and method to address regulatory requirements, such as those described in the ED112 document, that provide the requisite flexibility for recording voluntary parameters while simultaneously protecting the certification of the mandatory recording. Such new system and method for building and certifying a mandatory flight data recording system would provide the flexibility of permitting changes to be made to the recorded parameter set without the need for re-certifying the mandatory parameter recording aspect of the recording system.
It is known in the art to merge data recording streams in situations where it is necessary to certify the recorded flight data, or where the merged stream has been certified as a fixed non-flexible set of parameters comprising the flight data. There is a need in the art, however, for a system and method of injecting of an uncontrolled and uncertified voluntary recorded flight data stream into the mandatory and certified recorded flight data stream to add some flexibility to the certification of the mandatory recording function.